(原創) derived-class要怎麼呼叫base-class的constructor? (.NET) (C#)
Abstract
有時我們在derived-class的constructor提供的參數，事實上是base-class的資料，或者base-class根本就是ABC(abstract base class)，這時我們就得在derived-class的constructor去呼叫base-class的constructor。
Introduction
1
/*
2
(C) OOMusou 2007 http://oomusou.cnblogs.com
3
4Filename : Constructor_CallBaseConstructor.cs
5Compiler : Visual Studio 2005 / C# 2.0
6Description : Demo how to call base class constructor
7Release : 02/16/2007 1.0
8
*/
9
using System;
10
11namespace CSharpLab
12{
13
class Student {
14 public string name;
15
16 public Student(string name) {
17 this.name = name;
18
}
19 }
20
21 class Bachelor : Student {
22 public string lab;
23
24 public Bachelor(string name, string lab) : base(name) {
25 this.lab = lab;
26 }
27
28 public static void Main() {
29 Bachelor bachelor = new Bachelor("John", "PECLab");
30 Console.WriteLine(bachelor.name);
31 Console.WriteLine(bachelor.lab);
32 }
33 }
34}
/* 
2
(C) OOMusou 2007 http://oomusou.cnblogs.com3
4
Filename : Constructor_CallBaseConstructor.cs5
Compiler : Visual Studio 2005 / C# 2.06
Description : Demo how to call base class constructor7
Release : 02/16/2007 1.08
*/9
using System;10
11
namespace CSharpLab12
{
13
class Student {
14
public string name;15
16
public Student(string name) {17
this.name = name;18
}19
}20
21
class Bachelor : Student {22
public string lab;23
24
public Bachelor(string name, string lab) : base(name) {25
this.lab = lab;26
}27
28
public static void Main() {29
Bachelor bachelor = new Bachelor("John", "PECLab");30
Console.WriteLine(bachelor.name);31
Console.WriteLine(bachelor.lab);32
}33
}34
}
執行結果
JohnPECLab
24行的constructor提供了兩個參數，name為base-class的資料，而lab為derived-class的資料，所以勢必呼叫base-class的constructor才行，C#的方式是在constructor initializer list使用base keyword，並帶入參數，這樣就可以執行base-class的constructor了。
C++是在constructor initializer list呼叫base-class的constructor，而Java是在body中使用super這個keyword。
See Also
(原創) derived-class要怎麼呼叫base-class的constructor? (C/C++)
(原創) derived-class要怎麼呼叫base-class的constructor?(Java)
